Pain
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Comparative Study
Predictive validity of the Chronic Pain Coping Inventory in subacute low back pain.
The Chronic Pain Coping Inventory (CPCI) was developed to assess eight behavioral coping strategies hypothesized to be important for pain adaptation. But the predictive validity of the CPCI has yet to be tested in a longitudinal study. Here, 321 workers on sick leave after a work accident affecting the low back pain (LBP) region completed the CPCI during the subacute stage (T1) of LBP as well as the Catastrophizing scale of the Coping Strategies Questionnaire (CSQ). ⋯ Catastrophizing and Guarding were the most strongly associated with depressive mood at T1 but at T2, only depressive mood at T1 predicted this same variable. Results indicated also that the Guarding and Catastrophizing scales were able to predict future work status. The present study clearly reveals the usefulness of Guarding from the CPCI and Catastrophizing from the CSQ, when predicting different outcomes of adjustment to low back pain.
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Comparative Study Clinical Trial
Lack of sex differences in modulation of experimental intraoral pain by diffuse noxious inhibitory controls (DNIC).
The aims of this study were to investigate possible sex differences in (a) intraoral pain evoked by topical application of capsaicin to the gingiva, and (b) the modulation of this pain by diffuse noxious inhibitory controls (DNIC). Three groups with a total of fifty-four healthy volunteers (20 men, 20 women using oral contraceptives (W+OC), 14 women not using (W-OC)) completed the study. In two sessions, intraoral pain was evoked by topical application of 30microL 5% capsaicin to the gingiva. ⋯ The degree of modulation by DNIC did not differ between groups (P=0.636). In conclusion, for a superficial type of intraoral pain, only minor sex differences were found in pain intensity and no differences in the degree of endogenous modulation by DNIC. Female sex and the use of OC may not consistently be associated with higher sensitivity to pain.
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Comparative Study
Neuropathic pain: early spontaneous afferent activity is the trigger.
Intractable neuropathic pain often results from nerve injury. One immediate event in damaged nerve is a sustained increase in spontaneous afferent activity, which has a well-established role in ongoing pain. Using two rat models of neuropathic pain, the CCI and SNI models, we show that local, temporary nerve blockade of this afferent activity permanently inhibits the subsequent development of both thermal hyperalgesia and mechanical allodynia. ⋯ These results indicate that early spontaneous afferent fiber activity is the key trigger for the development of pain behaviors, and suggest that spontaneous activity may be required for many of the later changes in the sensory neurons, spinal cord, and brain observed in neuropathic pain models. Many pre-clinical and clinical studies of pre-emptive analgesia have used much shorter duration of blockade, or have not started immediately after the injury. Our results suggest that effective pre-emptive analgesia can be achieved only when nerve block is administered early after injury and lasts several days.
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Comparative Study
Comparative actions of the opioid analgesics morphine, methadone and codeine in rat models of peripheral and central neuropathic pain.
Controversy persists in relation to the analgesic efficacy of opioids in neuropathic pain. In the present study the effects of acute, subcutaneous administration of the mu-opioid receptor agonists morphine, methadone and codeine were examined in rat models of peripheral and central neuropathic pain. In the spared nerve injury (SNI) and chronic constriction injury (CCI) models of peripheral neuropathic pain, both morphine (6mg/kg) and methadone (3mg/kg) attenuated mechanical allodynia, mechanical hyperalgesia and cold allodynia for up to 1.5h post-injection (P<0.05); codeine (30mg/kg) minimally alleviated mechanical hypersensitivity in SNI, but not CCI rats. ⋯ The therapeutic window (based on antiallodynia versus ataxia) obtained for codeine, was vastly superior to that obtained with morphine or methadone in SNI and SCI rats. Furthermore, the therapeutic window for codeine in SCI rats was 4-fold greater than in SNI rats. Our results further support the efficacy of mu-opioid receptor agonists in alleviating signs of neuropathic pain in animal models of peripheral and especially central nerve injury.
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Comparative Study
Calcitonin gene-related peptide enhances TTX-resistant sodium currents in cultured dorsal root ganglion neurons from adult rats.
The neuropeptide calcitonin gene-related peptide (CGRP) binds to a subpopulation of dorsal root ganglion (DRG) neurons, elevates intracellular calcium, and causes inward currents in about 30% of lumbar DRG neurons. Using whole-cell patch clamp recordings, we found in the present study that application of CGRP to isolated and cultured DRG neurons from the adult rat enhances voltage-gated TTX-resistant (TTX-R) Na(+) inward currents in about 30% of small- to medium-sized DRG neurons. During CGRP, peak densities of Na(+) currents increased significantly. ⋯ The effect of CGRP was also blocked after bath application of PKA14-22, a membrane-permeant blocker of protein kinase A, and PKC19-31, a PKC inhibitor, in the recording pipette. These data show pronounced facilitatory effects of CGRP on TTX-R Na(+) currents in DRG neurons which are mediated through CGRP receptors and intracellular pathways involving protein kinases A and C. Thus, in addition to prostaglandins, CGRP is another mediator that affects TTX-R Na(+) currents which are thought to occur mainly in nociceptive DRG neurons.